DC and AC Electric Field Measurements by Spin-Plane Double Probes Onboard MMS

Friday, 18 December 2015
Poster Hall (Moscone South)
Per-Arne Lindqvist1, Goran Tage Marklund1, Yuri V Khotyaintsev2, Robert E Ergun3, Katherine Goodrich3, Roy B Torbert4,5, Matthew R Argall4 and Rumi Nakamura6, (1)KTH Royal Institute of Technology, Stockholm, Sweden, (2)IRF Swedish Institute of Space Physics Uppsala, Uppsala, Sweden, (3)University of Colorado, Boulder, CO, United States, (4)University of New Hampshire, Durham, NH, United States, (5)Southwest Research Institute, San Antonio, TX, United States, (6)Space Research Institute, Austrian Academy of Sciences, Graz, Austria
The four spacecraft of the NASA Magnetospheric Multiscale mission (MMS) were launched on 12 March 2015 into a 1.2 x 12 Re equatorial orbit to study energy conversion processes in Earth's magnetosphere. After a 5-month commissioning period the first scientific phase starts on 1 September as the orbit enters the dusk magnetopause region. The Spin-plane Double Probe electric field instrument (SDP), part of the electric and magnetic fields instrument suite FIELDS, measures the electric field in the range 0.3 - 500 mV/m with a continuous time resolution up to 8192 samples/s. The instrument features adjustable bias currents and guard voltages to optimize the measurement performance. SDP also measures the spacecraft potential, which can be controlled by the Active Spacecraft Potential Control (ASPOC) ion emitter, and under certain conditions can be used to determine plasma density. We present observations of DC and AC electric fields in different plasma regions covered by MMS since launch including the night side flow braking region, reconnection regions at the dusk and dayside magnetopause, and in the magnetosheath. We compare the electric field measurements by SDP to other, independent determinations of the electric field, in particular by the Electron Drift Instrument (EDI), in order to assess the accuracy of the electric field measurement under different plasma conditions. We also study the influence of the currents emitted by ASPOC and EDI on the SDP measurements.